Bibliographic details of the publications referred to by author in, this specification are collected alphabetically at the end of the description.
Reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
The Australian Lung Foundation has reported that upper respiratory tract infections account for approximately 3-4 million visits to general practitioners (GPs) each year in Australia, costing taxpayers more than AU$150 million in direct cost and considerably more in indirect costs. Lower respiratory tract infections account for almost 3 million visits to GPs each year in Australia. The social and economic impact is further compounded by the number of hospitalizations attributed to respiratory infection. For example, community-acquired pneumonia is associated with an overall mortality rate in Australia of approximately 12% per annum for hospitalized patients aged greater than 65 years. This mortality rate increases to approximately 20% if co-morbid diseases are present (e.g. chronic obstructive pulmonary disease, congestive cardiac failure, diabetes). Furthermore, up to 30,000 hospital admissions for asthma and up to 40,000 hospital admissions for chronic obstructive pulmonary disease are precipitated by viral infections, implicated in 50 to 80% of all hospitalizations for asthma and chronic obstructive pulmonary disease. As a result, the direct and indirect cost burden of in Australia is estimated to be more than AU$500 million each year.
Etiological agents associated with respiratory infection can be classified into bacterial (including Bordetella pertussis), fungal and viral. Influenza types A or B viruses cause epidemics of disease almost every winter. Seasonal vaccinations (flu shots) can prevent illness from Influenza Types A and B, but do not protect against Influenza Type C. Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in infants and young children, with the majority of hospitalizations occurring in infants less than 1 year of age. Worldwide, RSV is believed to be associated with an annual mortality rate of 160,000-600,000 deaths. Those at increased risk of severe RSV disease include premature infants, and infants with congenital heart disease, neuromuscular disease, structural airway abnormalities and immunodeficiencies. Human parainfluenza viruses (HPIVs) are second only to RSV as a common cause of lower respiratory tract disease in young children. HPIVs can also cause serious lower respiratory tract disease with repeat infection, including pneumonia, bronchitis, and bronchiolitis, especially among the elderly and among patients with compromised immune systems.
Despite the magnitude of respiratory diseases worldwide, treatments are primarily supportive in nature. The use of bronchodilators, corticosteroids and leukotriene receptor antagonists (e.g. montelukast) has generally failed to demonstrate conclusive clinical benefit and antiviral drugs such as ribavirin have demonstrated only marginal clinical benefit. Current approaches to the treatment and prevention of respiratory infections include second-generation monoclonal antibodies and the highly potent antiviral compounds such as Oseltamivir (Tamiflu [Registered Trade Mark]) and Zanamivir (Relenza [Registered Trade Mark]) for the treatment of Influenza. Vaccine compositions are also in development. However, the effectiveness of existing treatment regimes is largely dependent on identifying the respiratory pathogen in question. Unfortunately, given the large number of possible respiratory pathogens and corresponding strains, the use of standard diagnostics to identify a particular respiratory pathogen in a sample is time-consuming, costly and frequently leads to incorrect or inconclusive diagnoses. A typical diagnostic virology laboratory uses viral culture, immunofluorescence staining and polymerase chain reaction (PCR) to screen for respiratory viruses. However, existing techniques have significant limitations. For example, viral culture is time-consuming and lacks the requisite sensitivity for detection, particularly of viruses that are labile during transport and/or have fastidious growth requirements. Immunofluorescence staining is insensitive, often leading to false-negative results and current PCR assays typically lack the high-throughput detection capability to effectively handle a large number of samples containing multiple targets.
There is a need to develop an assay to screen for multiple respiratory pathogens with a high level of rapidity and sensitivity.